1. FIELD OF THE INVENTION
The present invention generally relates to clamps used to interconnect pipe sections of an automotive exhaust system. More specifically, this invention relates to a method for forming a clamp saddle for a U-bolt clamp, wherein the method provides a relatively low cost manufacturing process which is suitable for use in mass production, and the clamp saddle produced thereby is structurally strong yet sufficiently resilient so as to be able to accommodate variations in pipe size and hardness.
2. DESCRIPTION OF THE PRIOR ART
Automotive exhaust systems are conventionally composed of several pipe sections which interconnect the engine's exhaust manifold with one or more mufflers. While original equipment and aftermarket exhaust systems may be of a unitary design in which the system's components are welded together, it is not uncommon that the individual components of an exhaust system are held together by telescoping one pipe section within its mating pipe section, and then securing the components together with a clamp.
Various forms of clamps have been especially developed for the purpose of clamping exhaust components together. A common example is the U-bolt clamp, which is generally composed of a U-shaped bolt and a U-shaped saddle. The ends of the U-shaped bolt are threaded and, when inserted through a pair of holes or channels formed in the saddle, the U-bolt and saddle together form a circular passage through which a pipe section can be received. The effective diameter of the circular passage is altered by the degree to which the threaded ends of the U-bolt project through the channels in the saddle. Tightening a nut on each threaded end of the U-bolt enables the U-bolt clamp to generate a clamping load on the pipe sections received in the circular passage. In doing so, a pair of nested pipe sections can be sufficiently collapsed around each other so as to secure the pipe sections together and form a seal between the pipe sections which is sufficient to substantially prevent the escape of exhaust gas.
U-bolt clamps must be capable of generating a significant clamping load in order to reliably secure two exhaust components through numerous thermal cycles while exposed to a corrosive environment. Consequently, the design of a U-bolt clamp, and particularly the U-bolt saddle, must be structurally strong, yet must be sufficiently resilient in order to be able to accommodate variations in pipe size and hardness. Accommodating some deviation in pipe size is essential in order for the U-bolt clamp to reliably seal the joint formed by the pipe sections being clamped. In addition, the accommodation of such variations avoids the requirement for a uniquely sized U-bolt clamp for every exhaust system manufactured as original or aftermarket equipment.
Due to the relatively complicated structural requirements of the saddle, a further reduction in the manufacturing costs of a U-bolt clamp design necessitates a relatively low cost manufacturing process for the saddle which is suitable for use in mass production. Achieving a suitable compromise between strength, adaptiveness and cost is a continuing challenge for manufacturers of these devices. Accordingly, many variations of U-bolt clamps have been suggested in the prior art. One such variation involves forming the saddle from two members which are permanently fastened together to form a unitary saddle. Examples of this approach are illustrated in U.S. Pat. No. 2,719,345 to Riker, U.S. Pat. No. 3,055,072 to Brown, U.S. Pat. No. 4,040,152 to Gilgallon, and U.S. Pat. No. 4,488,334 to Goforth. Each of these approaches teach welding the half members together to form the desired unitary saddle structure. Notably, the teachings of Goforth are directed toward a rigid saddle structure which exhibits a slight degree of yieldability in order to provide a reliable connection between pipe sections even when variations in pipe size and shape exist. Goforth contrasts saddle structures of the type taught by Gilgallon, characterizing them as being excessively rigid, such that variations in the size and shape of pipe sections cannot be readily conformed to during clamping. Goforth teaches that excessive rigidity results in reduced radial deflection and a less reliable sealing of the joint formed by the pipe sections.
The clamping capability achieved by the U-bolt clamp taught by Goforth achieves a desirable balance of the strength and adaptiveness requirements noted above. However, the manufacturing and assembly of two individual members to form the saddle can be disadvantageous from the standpoint of processing costs and complexity, in that two individual components must be formed, accurately positioned relative to each other, and then welded together in order to form the desired unitary saddle structure.
Accordingly, the prior art also includes suggestions which advocate the formation of the saddle from a unitary stamped piece. Examples of this approach are illustrated in U.S. Pat. No. 3,192,593 to Osborn et al., U.S. Pat. No. 3,772,745 to Dowling et al., U.S. Pat. No. 4,122,586 to Nothdurft, U.S. Pat. No. 4,229,863 to Bowden et al., and U.S. Pat. No. 4,265,005 to Heckethorn. Each of these approaches teach forming the saddle from a metal blank which is folded over on itself to form mating halves of a unitary saddle structure. Osborn et al. illustrate such an approach in its more basic form, in which the mating halves are secured in a face-to-face relationship. Dowling et al. teach the addition of a flange in order to reinforce the saddle and prevent its buckling during tightening of the U-bolt nuts. Similarly, Nothdurft teaches the forming of reinforcing ribs in the saddle to resist bending of the saddle. Heckethorn teaches the combination of a reinforcing rib and flange in order to stiffen the saddle. Finally, Bowden et al. teach that forming the saddle to have a U-shaped cross section, as opposed to the face-to-face configuration taught by Osborn et al., Dowling et al., Nothdurft, and Heckethorn, enhances the strength of the saddle.
However, as taught by Bowden et al., saddles such as that taught by Osborn et al. and Dowling et al. are not sufficiently rigid to adequately secure exhaust pipe sections together. At the other extreme, Goforth notes that saddles such as that taught by Nothdurft are excessively rigid to suitably accommodate variations in size and shape of the pipe sections. Goforth also notes that excessive size of the saddle is undesirable from the standpoint of installation. Such appears to be the case with Nothdurft and Bowden et al.
From the above discussion, it can be readily appreciated that the saddle structure taught by Goforth has structural and functional advantages over other saddle designs known in the prior art. However, the two-piece design taught by Goforth can be disadvantageous from the standpoint of processing costs and complexity.
Accordingly, what is needed is a cost-efficient U-bolt clamp for clamping two pipe sections of an automotive exhaust system together, wherein the U-bolt clamp is structurally strong, yet exhibits sufficient resiliency so as to be able to accommodate variations in pipe size and hardness, while simultaneously requiring a relatively uncomplicated forming operation to achieve the desired results.